The field of left-right (LR) asymmetry is currently at an exciting point, with considerable body of genetic and cell-biological data elucidating dozens of mechanisms in a range of vertebrate and invertebrate model species. The patterning of the LR axis can conceptually be broken down into several distinct steps that have served as a working model for the field. The embryo orients the LR axis with respect to the dorsal-ventral and the anterior-posterior axes, hence being able to "tell its left from its right". Next, the embryo must set up a stable biophysical or molecular difference between the left and right sides, which can be imposed upon multicellular fields as the embryo divides. Third, cell fields on the left and right sides execute transcriptional cascades that set up differential gene expression patterns impinging on organ primordia. Fourth, the various organs make use of this asymmetric information as they undergo asymmetric morphogenesis.